Currently, an optical time domain reflectometer (OTDR) is widely used for optical fiber line fault location. The OTDR is a precise photoelectric integration instrument made by means of back scattering generated by Rayleigh scattering and Fresnel reflection of a ray propagating in an optical fiber, is widely applied to maintenance and construction of optical cable lines, and is mainly used to measure a length of an optical fiber, propagation attenuation of the optical fiber, connector attenuation, fault location, and the like. However, a conventional OTDR is a handheld device. Using the OTDR as a test instrument is a scattered and passive manual maintenance means, higher optical fiber security requirements can be hardly ensured, and the OTDR is expensive. When a fault in an optical fiber line is determined, a worker needs to enter a station and switches off the optical fiber line to perform a test. A long location period and a long time of service interruption cause a relatively great economic loss.
To perform OTDR probe in time, the prior art proposes that the OTDR is directly made into an independent unit to be integrated in a device. As shown in FIG. 1, an OTDR unit uses a wavelength independent from a service unit and an optical supervisory unit, is connected to a multiplexing/demultiplexing unit, and may implement real-time online optical fiber status detection unidirectionally. However, for an optical add/drop multiplexer(OADM) station in a WDM system, to implement OTDR probe on optical fibers in an entire network, an OTDR unit needs to be configured for an egress in each direction. Therefore, not only many units are configured, but also a large amount of cabinet space or device slots need to be occupied. Consequently, device costs and installation costs are both very high.
To avoid configuring an OTDR unit for an egress in each direction, the prior art proposes that an OTDR unit is integrated in a station and a multipath optical switch for the OTDR unit is added to monitor optical fiber alarms in multiple directions in real time, thereby reducing costs for configuring OTDR units in multiple directions. However, real-time online optical fiber status detection cannot be implemented and line assembly is relatively complex.
Therefore, it can be known that the foregoing two solutions are both solutions in which an OTDR is used as an independent unit and integrated in a station, and does not share a wavelength with a service unit or an optical supervisory unit. Further, the foregoing two solutions need to modify an existing system card, for example, adding an access port of an OTDR unit to a multiplexing/demultiplexing unit. The integrated OTDR is an independent unit. Installation of the OTDR unit occupies space of a cabinet or a device slot, and has high costs.